Extended Data Figure 5 : Coupled voltage and calcium dynamics mapped during ventricular fibrillation.

From: Electromechanical vortex filaments during cardiac fibrillation

Extended Data Figure 5

Voltage (action potential, green, voltage-sensitive staining using Di4-ANBDQPQ) and calcium (intracellular calcium, orange, calcium-sensitive staining using Rhod2-AM) vortex wave activity mapped on ventricular surface of the isolated rabbit heart during ventricular fibrillation using dual-imaging29. Recordings were acquired in non-contracting hearts after administering of blebbistatin (4 ml diluted in 700 ml Tyrode, retrograde perfusion with constant reperfusion). a, b, Example time-series (n = 5) of voltage–calcium activity chosen from arbitrary sites on the surface. Time-series show closely coupled voltage–calcium wave dynamics with a dominant frequency of 9 ± 1 Hz and a delay of the calcium activity. a, Activity on the surface within 2 s long (left) and 1 s long intervals (right) to facilitate viewing of the upstrokes and the delay between voltage and calcium. Recordings acquired before administering (a) and after the addition of cromakalim (b, 10 μmol in 1 l Tyrode, retrograde perfusion with constant reperfusion). We did not observe a noticeable difference in the dynamics. c, Voltage (action potential, green, voltage-sensitive staining using Di4-ANBDQPQ) and calcium (intracellular calcium, orange, calcium-sensitive staining using Rhod2-AM) raw movies (black-and-white colour code) mapped on ventricular surface (field of view approximately 1.5 × 1.5 cm2, time in ms) during ventricular fibrillation. The voltage-sensitive data are inverted (dimensionless normalized units (n.u.)), such that bright (or green) areas show depolarized tissue. Bright (or orange) areas in the calcium-sensitive data (dimensionless normalized units (n.u.)), show high intracellular calcium concentrations. The calcium-sensitive images show the same part of the tissue that is shown in the voltage-sensitive images, however, with a delay of 10 ms to compensate for the delay between voltage and calcium and to facilitate analysis of similar wave patterns. The patterns are highly similar and evolve congruently across the surface during ventricular fibrillation. Example image series chosen from a recording with a duration of 20 s. The findings are the same across different recordings. The experiment was repeated twice in n = 2 hearts. However, other studies41,42,43,44 have also shown that in abnormal voltage and calcium regimes the dynamics can have complex interactions and are not always necessarily closely coupled as shown here (see also Supplementary Discussion).